This is an audio-visual and cinematographic work, and 50 years have passed since the year of its creation (that is, the work was made before 1974)
This is an anonymous or pseudonymous work, and 50 years have passed since the year of its creation or publication (that is, the relevant action was done before 1974)
This is a work of the government and 50 years have passed since the date when the work was published or first made available to public (that is, the relevant action was done before 1974)
This is a work of applied art and 25 years have passed since the year of its creation (that is, the work was made before 1999)
This is another kind of work, and 50 years have passed since the year of the author's death or last-surviving author's death (that is, the death occurred before 1974)